From 226ec5f51acb6fdf651e2498be69c0f8d8b7ce3f Mon Sep 17 00:00:00 2001
From: Michael Mainguy <mike.mainguy@gmail.com>
Date: Sat, 29 Nov 2025 08:17:14 -0600
Subject: [PATCH] Fix bullet trajectory when ship is rotating
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Calculate velocity at bullet spawn point (8.4 units from center) instead
of ship center. Accounts for tangential velocity from angular rotation
using cross product: velocity_at_spawn = linear + (angular × offset).

This fixes bullets appearing to drift when ship is moving and rotating.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
---
 src/ship/ship.ts         | 24 +++++++++++++++++++++---
 src/ship/weaponSystem.ts |  2 +-
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/src/ship/ship.ts b/src/ship/ship.ts
index 8680ac0..117c3a7 100644
--- a/src/ship/ship.ts
+++ b/src/ship/ship.ts
@@ -697,11 +697,29 @@ export class Ship {
         }
 
         if (this._weapons && this._ship && this._ship.physicsBody) {
-            // Calculate projectile velocity: ship forward + ship velocity
-            const shipVelocity = this._ship.physicsBody.getLinearVelocity();
+            // Get ship velocities
+            const linearVelocity = this._ship.physicsBody.getLinearVelocity();
+            const angularVelocity = this._ship.physicsBody.getAngularVelocity();
+
+            // Spawn offset in local space (must match weaponSystem.ts)
+            const localSpawnOffset = new Vector3(0, 0.5, 8.4);
+
+            // Transform spawn offset to world space (direction only)
+            const worldSpawnOffset = Vector3.TransformNormal(
+                localSpawnOffset,
+                this._ship.getWorldMatrix()
+            );
+
+            // Calculate tangential velocity at spawn point: ω × r
+            const tangentialVelocity = angularVelocity.cross(worldSpawnOffset);
+
+            // Velocity at spawn point = linear + tangential
+            const velocityAtSpawn = linearVelocity.add(tangentialVelocity);
+
+            // Final projectile velocity: forward direction + spawn point velocity
             const projectileVelocity = this._ship.forward
                 .scale(200000)
-                .add(shipVelocity);
+                .add(velocityAtSpawn);
 
             this._weapons.fire(this._ship, projectileVelocity);
         }
diff --git a/src/ship/weaponSystem.ts b/src/ship/weaponSystem.ts
index 3d35419..cc6855a 100644
--- a/src/ship/weaponSystem.ts
+++ b/src/ship/weaponSystem.ts
@@ -83,7 +83,7 @@ export class WeaponSystem {
         // Create projectile instance
         const ammo = new InstancedMesh("ammo", this._ammoBaseMesh as Mesh);
         ammo.parent = shipTransform;
-        ammo.position.y = 0.1;
+        ammo.position.y = 0.5;
         ammo.position.z = 8.4;
 
         // Detach from parent to move independently